Pneumatic tired wheels are widely used in virtually all types of land vehicles, including automobiles, trucks, trailers, tractors, and other self propelled and unpowered vehicles, and aircraft landing gear. The intense development activities involving pneumatic tired wheels and tires has resulted in a highly developed state of the art with respect to tire design, composition, function and reliability.
The performance of pneumatic or gas charged tires is substantially degraded by the loss of inflation pressure. Various attempts have been made to eliminate loss of charge pressure due to tire wall puncture and provide tire designs that will enable the tire to continue to operate in a deflated or “run-flat” condition ranging from modification of tire design to introduction of materials and devices within the tire cavity to support the tire during a deflation period.
Typical run-flat technology utilizes a passive approach where a solid mass supports a load in a run-flat condition. During such a condition, the rotating tire material, e.g., urethane, does not respond normally and a hysteresis develops which causes heat stress conditions. At particular frequencies, the rotating tire material reacts slowly to the applied forces and “lags” or does not completely return or rebound to its original state. The applied forces at particular frequencies above a threshold deform the rotating tire material and internal elastic and frictional stresses are produced, which result in energy lost to heat and the aforementioned heat stress conditions. Accordingly, there is a need for run-flat technology which minimizes heat hysteresis and heat stress conditions.